Corrosion preventing attachment for boats



March 7, 1933. I| l DURHAM CORROSION PREVENTING ATTACHMENT FOR BOATS Filed June 23, 1931 INVENTOR HHHOLDDa/ef/ n l ATTORNEY Patented Mar. 7, 11933V `UNITED STATES PATENT oFFlcE HAROLD L. DURHAM, 0F EVERETT, WASHINGTON 'Application led June 23,J

rlhis invention relates to a method of and means for preventing electrolysis and it has reference in particular to the application of this method and means to motor or engine driven boats which operate in salt or sea water, although not limited to boats; it being the principal object of the invention to provide an economical and satisfactory means for overcoming that undesirable and destructive corrosion or eating away of parts exposed to the water, such as the propellerl shaft, the rudder post and bushings, that is caused by galvanic or electrolytic action resultant to the use of di'erent metals in the boat, bearings, bushings, shafts, etc., and their contact with salt water.

Explanatory to the present invention, it will here be stated that considerable damage is done to boats operating in salt water, due to this galvanic or electrolytic action, and it is required that the bushings and bearings which support the propeller shaft and rudder quite frequently be replaced; also it often happens that the propeller shaft and the rudder shaft will be eaten away adjacent their supporting bearings and this will finally result in their breaking off. Also, rivets are eaten away and propellers and rudders also become pitted and damaged. As ageneral rule bushings used in these positions are of v brass or bronze, and the shafts which operate therein are of steel, while the propeller and rudder are of brass or bronze. These diiferent metals, operating in salt water, produce an action that is exactly analogous to the action of a primary 1iattery in which a piece of zinc and a piece of carbon are immersed in an electrolite and connected through an external circuit. In such a case one of the metals corrodes and is carried to the other, on which it is'deposited.

This action of electrolysis has been overcome in the present invention by effectingv a change of polarity so that those parts ordinarily a'ected, such as rudders, propellers,`

bushings, etc., become the negative poles instead of positive. This change is effected by electrically connecting Aall those parts affected b electrolysis in a circuit with one or more zinc plates, exposed to the salt water and of 1931. Serial N'o. 546,285.

suicient size to be effective as positive anodes in the circuit. These plates of zinc are contamed in bronze bases, which in turn are electrically connected tothe metallic parts with- 1n the boat, such as the hull, engine housing, 55 propeller shaft and bushings, in such manner that the zinc plates will charge oii' into the water instead of the usual corrosion of bearings, bushings-or shafts of the operating parts; it being provided that the zinc plate may be replaced as often as is neces'- sary.

Other objects of the invention reside in the various details of construction, the combination of parts, and their mode of use, as will hereinafter be described.

In accomplishing the objects of the invention, I have provided the improved details-of construction, the preferred forms of which are illustrated in the accompanying drawing wherein- Fig. l is a sectional detail of a ortion of a boat, diagrammatically illustrating the location of the engine propeller and drive shafts, and also the disposition of the zinc plate and its connection with the engine in accordance with the present invention.

Fig. 2 is an enlarged sectional view of the zinc plate and its mounting base.

Fig'. 3 is a plan view. y

Fig. 4 is a sectional detail showing the corrugated surfaceof the plate.

Referring more in detail to the drawing-- l designates what may be a boat of the ordinary wooden hull type used for pleasure 8.5 or for fishing or other commercial purposes;

2 designates the engine, 3 the propeller shaft which extends from the engine rearwardly through a stern bearing 4, and which, at its end, mounts a lpropeller 5. Supported reari Wardly of the propeller, by means of a vertical shaft 6 extended through mounting bearings 7, is a rudder 8.,

As was previously stated, boats not equipped with the electrolysis eliminating zinc plate and its circuitV connections, are damaged by the electrolytic action incident to use of different metals in salt water. This damage as a rule shows in the corrosion of the propeller shaft adjacent the stern bearing,

' quired that the shaft and shaft l rudder shaft and bearings.

4 screws 13. 1t is 'lo overcome the undesirable corrosion, ll

have provided a circular plate or disk ofl zinc 12. 'llhis is detachably lixed by means of a plurality of screws 13 within a base late 14 of bronze. The base has a central liess 15 on its back side for receiving a bolt 16 for securing it to the boat hull, and a circuit connection 17 extends from the bolt and is grounded to a metal portion of the engine or to a bearing within the boat in which the propeller shaft is carried. ln the event that the hull is of metal, the bronze base must be properly insulated from it. lt will be apparent that with this arrangement, any current that is created will iow from the zinc plate across the intervening space between the plate and the propeller, `rudder or their shafts, and will then return to the engine land through the short circuit 17 back to the lplate. This direct connection with the engine eliminates circuit passing from the shaft adjacent the stern bushing and then through bushing and the stern bearing, thus causing `corrosion of the shaft and'destruction to ad- .Ljacent parts. When the zinc plate has been eaten away it may be removed for replacement simply by removing its supporting referred that the surface of the zinc late be corrugated, as at 12' in Fi 4, as t s provides more surface.

xperience has roven the value of this invention. lt, has een found that when it is in use, there is no destruction to the propeller shaft or its bearings, and that the only noticeable corrosion is in the zinc plate. 'llhe proof of this action is found in the fact that the propeller, shaft and rudder will be plated with the zinc.

`lltI is to be understood that the drawing is only illustrative of the use of the method, and that as 'many of the zinc plates may be 'used as are found to be necessary, in order to change the polarity of those arts which, *without use of the plates, woul bethe ositive anodes of the circuit.. rlhese p ates would be placed at various places, and meters could be employed 'in the circuit to indicate the extent to which the method was eective.

rllhe essence of the invention, as above described, is thought to reside in the connecting up, by copper wire or the like, of all affected parts exposed to the salt water, with one or more of the eliminator V are exposed to the salt water which serves ias the electrolyte. 'llhe use of these zinc plates reverses the normal dow of current so that parts normally aected become negative and receive the zinc deposit.

'llhe principal point to consider in carrying out the method is to make sure that all parts aected by electrolysis will be properly in circuit.

plates of zinc which' recaen principally in its application to boats operating in salt water, it is not the intention that the invention be limited in use only to boats, but that it be applied wherever electrolysis occurs and where the method can conveniently be employed. lln this respect l have reference to overcoming electrolysis in pumps operating in salt water; also various machines connected with sewers and the like, in which electrolysis occurs by reason of the use of various metals in a conducting electrolyte.

Having thus described my invention, what l claim as new therein and desire to secure by Letters-Patent is:

1. In a boat designed for operation in salt water and having a stern bearing and propeller shaft extending therethrough, a zinc plate attachedy to the hull ofthe boat and in contact with the water in which it floats and having a circuit connection with the propeller shaft at a point within the stern bearing.Y

2. lin a boat designed for operation in salt water and having a stern bearing, a propeller shaft extending through the bearing and an engine in the boat operatively connected with the shaft, a bronze base plate attached to the hull of the boat outside and beneath the water, a zinc plate mounted within said base plate and exposed to the water, and a circuit connection between the zinc plate and engine.

3. A device as in claim 2 wherein the zinc plate is removably mounted in the base plate.

a circuit therethrough ed at Everett, Snohomish County, 

